Electric drive



May 25, 1948. R. R. BAKER 2,441,985

ELECTRIC DRIVE Filedoct. so, 1946 eo W G lx o wlTNEssEs; N

@72/ Y Ee A?, B ker. @zu 9 BY ATTORNEY ing;

Patented May 25, 1948 UNITED STATES 2,441,385 ELECTRIC DRIVE Rest R. Baker, Pttshurghla., assi gnor .to .Westv",inghouse Electric Corporation; East Pittsburgh Pa., a corporation of Pennsylvania- Application october so, 1946; serial Np. 106,756

end section in which the paper stock consoldates .andpecomes sufficiently self-sustainingto be sub- .iected to a creping Idevice -be'fore it'enters the drying 4section Qf the maehnery- 'lhe @ming section of the machine must be driven at a higher speed than the drying section in `ordert') ,talee care of the shrinkage in length caused bythe crevice procedure.

It is enbbiet Qf my invention to merid@ en electric drive `for crepe-forming paper machines in Vwhichlthe operating speeds of the forming ,nddrying sections are a tomatically and accurately maintained in va given or selected ratio in accordance with a'desired percentage of' crepging, and which permits adjusting .the speed 'of thevforining section Withoutaffecting the selected percentage of creping.

{10 this end, and in accordance with a feature crine' invention, Ifprdvide a' generator' which is drivenpythe variable speed motor of the forinsing section and energizes the drive motor of "the drying sect1on, so Ithat the speed ofthe drying section depends on the speedof the forming section .and n thefield excitation of the generator.

andfan'adjustable rheostat or theflike impedance ispreferably arranged in one of theeld circuits of the control generator to permit selecting the percentage of creping.

.l These .and othenobjects and features lof myinyen'ton VWillvloeapparent yfrom the following descriptionpfthe .embodiment shown Sin' the draw- `".The ,drawing represents schematically some ,parts of. a creping paper machine in conjunction `ftvit'h the `circuitdiagram 'of an appertaining elec- Ltxjic dfrveaccordingto the invention.

.Inlthe 'machinery illustrated on'V the drawing, a

group vlof pulp nozzles "I depositsthe paper Vstock lstock nearly s prenne and drying operateur. The stock the 6 is supported and guidedby anumber of rollers issiiilarly supported eed Yguided by rleis' vSuch as those denotedby Il and l2, The rollers `9 and I l form together La ollpjess. As the stock-trav- Qient liquid is removedtherefrbin to 'render' the elf -supporting for the subsequent ,Des/.Ses @nio ,a dryer 'i611 Jvhieh ,frms .the last unit of the just A`desc rifbed"tiret-enti or forming section Of-ihejmahi- .fIjhe indivi-dual driven devices of the forming section ,are geared tota yline shaft l5 by means of suitable transmissions here schematically Mrpresented by a'fgear Vvfbox jl for ydriving 'the pulp screen roll 5, a 'fgdear box' "1.1 for 'driving thelb'ottom roll H of the roll press, a gearboxl for driving ithe end roll l-D f ofwthe gfeltl, and a'lgear box I Sin driving lconfnection with the dryer 'r'oll i3. line shaft" ifiis driven .through the gear l ox I6 from a reduction gear A2,0 tvhoseinput shaft-iscoupledto anelectric motor Ml." l

After the paper stock' has passed 'over most yof the periphery' of the Adryer 'roll `l 3', itis subjected to a `crepe doctor lilagdeg'ZS so that'the paper deflected fromthe roll 1 3 has the desired creped consistency. Asecond doctor b1ade`24 contacting the dryer roll l 3 serves to clean' it from resid- ,ual amounts off/stock." .The creped material passes intothe dryingsection Which includes a l'crepe set 'dryer 1,5, a 'group of drying rolls 16,;2] an'dl', and 'acalender'iepresented bthetwo rolls 4279 and .30. After leaving'the calender, the" flnished.' material 's'Y Wound onto a renal. line driven devices of the drying section vare gearedto a iine'fshaft32 by'jtrans- 'misfSQnS .which are schematically representejdl'by gear 'bcxeks`3,3,. 3.,4;p.35 H1362" .fljhe lirie' shaft 32 Oilllhe gearbox 1 35 fi's riveli v through aV reduction 'specic design and arrangement 'is not affeatu're ,Ofjhe ini/encontrara. rne invention as' such from respective generators, motor MI is denoted by 4| and an appertaining field winding by 42. Armature 4| is connected to the armature 43 of a generator GI which is driven at substantially constant speed by an auxiliary motor 44 and generates the motor load Voltage under control by a separately excited field winding 45.

The eld windings 42 and 45 are excited from direct current mains X and Y. These mains are energized by an exciter generator EX whose armature 46 is driven at substantially constant The armature of speed and to this end preferably mounted on theV shaft 47 of generator GI. The exciter EX has a series eld winding 48 and a shunt eld winding 49, and supplies mains X and Y with substantially constant voltage. A field rheostat is series-connected with motor field winding 42 between mains X and Y, and another field rheostat 52 is series-connected with generator field winding 45 between the mains. The two field rheostats 5| and 52 permit adjusting the speed of motor Ml to any desired value within the available range of speeds, for instance, between 90 and 330 rotations per minute. As customary, the sliders of the two rheostats may be ganged together in order to facilitate setting the adjustable voltage drive to the desired speed value.

The adjustable voltage for the drive motor M2,

of the drying section is provided by another generator G2 whose armature 53 is mounted on or geared to the shaft 54 of drive motor Ml. The voltage generated by armature 53 is controlled by two field windings 55 and 56. Field winding 55 receives constant excitation from mains X and Y through an adjusting rheostat 51, while iield winding 56 is excited by variable voltage from a control generator CG. The two eld windings 55 and 56 operate cumulatively. That is, the constant excitation of eld winding 55 is so adjusted that the minimum voltage generated in armature 53 is somewhat below the value corresponding to the minimum speed of motor M2, and the variable excitation applied to field winding 56 takes care of varying the voltage and speed within the required range.

The control generator CG has its armature 58 driven at substantially constant speed. To this end the armature, as illustrated, may be mounted on or connected to the shaft 41 of generator GI. Generator CG has three field windings 59, 60 and 6|. Winding 59, here shown as a series winding, is self-excited, while the windings 60 and 6| receive separate excitation of opposing directions, so that the field effects of windings 6D and 6| are differential and balanceable with respect to each other. The control generator CG is preferably of the amplifying type. In the illustrated example, the amplifying performance is obtained in the following manner. The circuit of the self-excited field winding 59 is so tuned that the resistance line of this circuit coincides approximately with the no-load saturation characteristic of the control generator. As a result, the self-excitation of the machine is sufficient to generate the desired output voltage and to maintain this voltage at any point along the straight portion of the voltage characteristic. Consequently, the resultant effect of the control field windings 66 and 6| is merely required to supply the impulse necessary for shifting the operating point of the machine along the straight portion of the characteristics. Thus, a very small amount of differential excitation to be supplied by eld windings 60 and 6| suiiices to change the output voltage of generator CG a proportionally large amount. The circuit devices for controlling the differential excitation of iield windings 6U and 6| will be described in a later place.

The armature "53 of generator G2 is connected through a switch or contactor 62 to the armature 63 of the drying section drive motor M2. The motor M2 has a field winding 64 excited from mains X and Y through a`calibrating rheostat 65. The adjustment of this rheostat is normally xed during the operation of the system so that the speed of motor M2 depends on the voltage generated in armature 53 of generator G2. This voltage, as will be understood from the foregoing, depends on two controlling factors, namely, on the speed of the drive motor M and on the eld excitation of generator G2. Since the excitation of generator field winding 55 is normally constant during the operation of the machine, the second factor for determining the speed of motor M2 is represented by the variable excitation of field winding 56 which, as explained above, depends only on the differential effect of field windings 60 and 6| in the control generator CG.

Field winding 66 is connected to the armature Si of a tachometer or pilot generator PI. Armature 61 is mounted on or geared to the shaft 54 of motor MI. The appertaining field winding 68 is excited by constant voltage so that the pilot voltage produced by pilot generator PI and imposed on the field winding 60 is proportional to the operating speed of motor MI, and hence of the forming section of the machinery.

Field winding 6| of generator CG is connected to the armature 69 of another tachometer or pilot generator P2 whose field winding is denoted by 7G. The armature 69 is mounted on or geared to the shaft of drive motor M2. Since field winding 10 receives constant excitation, the voltage of generator P2 changes in proportion to speed variations of motor M2, and the field winding 6| in generator CG is excited accordingly. The field windings 68 and 10 of respective pilot generators Pl and P2 are preferably seriesconnected to each other between the mains X and Y under inclusion of a series rheostat 1|. The application of such a series connection for the pilot generator field windings has the advantage of compensating the control equipment for slight temperature variations and for variations in exciter voltage because any such variations will affect the output of both pilot exciters to a substantially equal extent, and, since these two exciters feed two differentially acting fields of the control generator, the variations have substantially no disturbing effect on the control performance. A rheostat 'l2 is disposed in the circuit of eld winding 6|. This rheostat permits adjusting the excitation of eld winding 6| as regards its proportion to the voltage generated in the pilot exciter P2. In this manner the two field windings 60 and 6| can be made to balance each other at a desired speed differential of the motors MI and M2 in accordance with the intended percentage of creping.

Reviewing the performance of the machinery and the control system as a whole, it will be understood that in order to secure the desired degree or percentage of creping and a satisfactory constancy of the creped material, the speed of the drying section, driven by motor M2, must be maintained a given percentage below the speed of the forming section driven by motor M|. For instance, if a creping of 30% is required, and asthe speed" of motor MI.

QAM-,98o

ting" of rheostats' 5| 'and 52,'1 and with Switch or 'contacter 62'closed,

the voltagey generated bygenerator 'G2 'changes vsrlostan'ti'ally in proportionto l s s Iffmotcr M2'is running correctly at 'the ldesired speed, the excitation of field windings 60 and 6| 'is balanced, andthe -re- 'sultants'eld excitationlof., generator G2 constant. If inotor M2 vwere running' at alower speed than required, the voitage'impressed on field winding et would drop 'so that the nein or winding su becomes preponderant and causes the voltage of 25 generator CG to increase. This, in turn, increases the field excitation of generator G2 and causes the motor M2y toincrease its speed to the desired value. Conversely, at an excessive speed of motorA M2' the effectofliieldwinding 6| would dominate over' the countereifect'of iield winding 6D and then cause the'generator CG to reduce the excita- 'tion' of field windingr 56, thus causing the generator G2 to impress low voltage on m'otor M2. Consequently, the system operates Ato maintain the motor M2` accurately at a given speed diiierential relative'to motorMI. :Since this differential depends on the balanced'condition of windings 60 vand El, a change in thefadjustment oi rheostat "l2 has 'the effect of increasing cr' reducing'the 'diierential and hence the percentage of creping. It v/illl be understood by those skilled ,inv the art that electric drive Asystems according to ,the invention can be altered and vmodified' as regards various` details and with respect tospecic circuit connections without departing from the prin- 'ciples of `the invention, and within its essential 'features as set' forth in the claims attached hereto.

" I claim as my invention:

l. An electric drive for a creping paper machine having, a paper forming msectionanda drying section, comprising a .rst 'motor 'for the forming section, a generator having an armature mechanically connected withsaid 'nrst motor to' be driven Vtlie'rebyand having a neld Winding, aV second motor for the drying section, electrically connected to said generator varmature to y'loe energized therefrom in dependence upon the speed of said iirst motor and the excitation oi said field winding, two pilotgenerators mechanically connected to saidiirst andsecond motors to generate vtwo pilot voltages indicativey of the'speeds of said vrespective motors, a control generator operableat substantially constant speedand having an armature electrically connected to said ileld winding for controlling said excitation and having kiield meansconnected vto said two pilot generators 'to be energized independence upon the differential value of said pilot voltages in order to cause said iirst generator to operate said second motor substantially at a speed a given percentage below that -of said rst moto-r in accordance with a desired percentage of creping.

2. An electric drive for a creping paper machine having a paper forming' sec-tion and a crepe drying section, comprising aiirstmoto'ror the forming section, "ay genrtfhvng Aan a'rina't'ure mecnanicjauy' ctnrieetuj with 'said nrst" motor' to f5 'bediiven-therbyand havingf 'el'dvvinding'; a second'm'otor-"fr 'the 'drying section electrically connected to said generator armature to be energized therefrom dependence' upon the 'speed of said iirst"rn'otoi-v and the excitationof said ''eld vl0 Windirgftvvo pilotgneratfs,mechanically connectedto `s`aid^iirst`v and second'motrs to generate tw'o pilot voltages indicative `of` 'the speeds of l"said respective motors, 'a control vgeneratf'r operable at sabstantiaiiy epnstant"speeeanenaving enermature electrically' connec't'e'd :to said? field lvv ing for providing said 'excitation and 'two mutually balanceable contrlffeld' jwindings for diiefrent'iallyv controlling' saidL excitation, ,.s'ai'd"A 'control fieldv windings being .con 'ec'te'dfto` said'lpi'lo't' vvgen- 0 erators respectively to 'be energizedv by' Jsaid 'respective I'pilot Yvol'tages'- inffr'd'e'r to rcause said first :generator to operate said second'notor substantially' 'at a' speedl a given Apercentage `below that of'sa'idiirst 'nio-tor, and adjustaile'rhostat means diSPQSle'd.eiiieenfneff .'S'ai'd, pilot-'genrators and the appertainirig control held U{v'vinding 'to permit 'adjusting saidpercentage'iri'accordance with a desired n'rce'n'tage`-of` crepingl '-3. 'An' electric drive'ior a creiiirfigfpaperA machine having a' paper forming'section'andi'a v crepefdry- 'inesatta.comprising Mistificatore@ torming setta a generan j Yhatte f an 1 amature .mechanically connected with' an nist 'meer' to ,be dill/.en thefbif and hei/ing "B1 @ad ,Wfldigt a enhancer" fr'tHe, 'ne tetten. americain feonneetedte satdjgener'atplg armaturen pe ener- 'gized therefrom fi'n depelidle-nce'upon'i theyspeed for `rsaid n rstrntor andthe excitation of said nem @ll'g tir pilot ,geiiraters'haviig .lefs'ra'iive 40 i armatures mechanically connected toA saidirst een @centimeters and having electa een winaing' kfor, providing',v two; p ilot voltages f indicative of the speeds fof, saidy 'respective' Imotors,ineens ydispose'Cl'for .providing a Sli'b'stantiailyconstant win 'voltage and connected tosai'd two'frfi'eldfwindings of said respectivel pilot generators, said', latter windings being arranged in ,Series ,relation tb each other, 'a control Vge 'erator operable atsubstantial- 1y '.CQnStant Speed and, bevinden, armetureelec- `trolling said excitation and, having 'iield 4means '.CQleCtCd 't0 SedftWO p'lot" neratorltbe ,enei- 'giz'ed in dependencelupon the dilferentialjvalue oi "said pilot'voltage'si order to 'cause' said first4 generster ,topperate saidjjsecshdaiictor .substantially klata speed a; given percentage below lthat of'said 'rst 'motorin accordancewith a` desired percentjge 0f. tipping.' 4.' An electric driveior a creping paper machine :00 having a paper forrningl section Yand a. crepe dry- 1fling section', comprising afirstjmetdr fer Athe forming section, a generator having'anf'arniaturefme- "'chanicallyconnected with .saidiirstf motor tof be ,driven thereby` and 'a eliilwindi'nga seco5 Londrrictorrortne 'drying s'eg'zti'on` electrically Connected .to 'said' 'generator armaturel to 'l be. 'eher- 'g'i'z'ed therefrom independence`upon",the,sp.ed. of .1, .id 'rst vmotorfancl -thelexcitationL'o`t said 'field winding, "two 'pilot generators lhaving yrespective armatures mechanically connected to said rst and second motors and having each a ield winding for providing two pilot voltages indicative of the speeds of said respective motors, means disposed for providing a substantially constant voltage and connected to said two field windings of said respective pilot generators, said latter windings being arranged in series relation to each other, a control generator operable at substantially constant speed and having an armature electrically connected to said eld winding for providing said excitation and two mutually balanceable control eld windings for differentially controlling said excitation, said control field Windings being connected to said pilot generators respectively to be energized by said respective pilot voltages in order to cause said rst generator to operate said second motor substantially at a speed a given percentage below that of said iirst motor, and adjustable rheostat means disposed between the pilot generator appertaining to said second motor and the appertaining control eld winding of said control generator to permit selecting said percentage in accordance with a desired percentage of creping.

5. An electric drive for a creping paper machine having a paper forming section and a crepe drying section, comprising rst and second directcurrent motors for driving the forming and drying sections respectively, a main generator having an armature operable at substantially constant speed and electrically connected to said rst motor to supply adjustable voltage thereto, another generator having an armature mechanically connected to said irst motor and electrically connected to said second motor and having a eld winding, two pilot generators mechanically connected to said rst and second motors to generate two pilot voltages indicative of the speeds of said respective motors, a control generator having an armature mechanically connected to that of said main generator and electrically connected to said field winding, two mutually differential control field windings disposed on said control generator and connected to said respective pilot generators to control said control generator in dependence upon the diierential value of said pilot voltages in order to cause said other generator to operate said second motor substantially at a speed a given percentage below that of said iirst motor in accordance with a desired percentage of creping.

6. An electric drive for a creping paper machine having a paper forming section and a crepe drying section, comprising rst and second directcurrent motors for driving the forming and drying sections respectively, a main generator having an armature operable at sbstantially constant speed and electrically connected to said rst motor to supply adjustable voltage thereto, another generator having an armature mechanically connected to said rst motor and electrically connected to said second motor and having a iield winding, speed-responsive measuring means associated with said respective motors for providing two pilot voltages indicative of the speeds of said respective motors, a control generator operable at substantially constant speed and having an armature connected to said eld winding for providing variable excitation therefor and having eld means connected to said speed responsive means so as to control said excitation in dependence upon the differential value of said pilot voltages for causing said other generator to operate said second motor substantially at a speed a given percentage below that of said first motor in accordance with a desired percentage of creping.

'7. An electric drive for a creping paper machine having a paper forming section and a crepe drying section, comprising rst and second directcurrent motors for driving the forming and drying sections respectively, a main generator having an armature operable at substantially constant .speed and electrically connected to said first Imotor to supply adjustable voltage thereto, another generator having an armature mechanically connected to said first motor and electrically connected to said second motor and having a eld Winding, two pilot generators mechanically connected to said rst and second motors to generate two pilot voltages indicative of the speeds of said respective motors, said pilot generators having respective eld coils arranged in series relation to each other, a constant voltage exciter mechanically connected with said armature of said lmain generator and electrically connected to said series arrangement to provide excitation for said pilot generators, said exciter being also electrically connected to said main and other generators and said two motors to provide normally constant eld excitation therefor, a control generator having an armature mechanically connected to that of said main generator and electrically connected to said eld winding, two mutually differential control eld windings disposed on said control generator and connected to said respective pilot generators to control said lcontrol generator in dependence upon the differential value of said pilot voltages in order to cause said other generator to operate said second motor substantially at a, speed a given percentage below that of said first motor in accordance with a desired percentage of creping.

8. An electric drive for a creping paper machine having a paper forming section and a crepe drying section, comprising first and second directcurrent motors for driving the forming and drying sections, respectively, a main generator having an armature operable at substantially constant speed and electrically connected to said rst motor to supply adjustable voltage thereto, another generator having an armature mechanically connected to said rst motor and electrically connected to said second motor and having a field winding, two pilot generators mechanically connected to said rst and second motors to generate two pilot voltages indicative of the speeds of said respective motors, a control generator having an armature operable at substantially constant speed and connected to said field winding to provide excitation therefor, said control generator having two opposingly acting control eld windings connected to said pilot generators respectively for controlling said excitation in order to cause said other generator to operate said second motor substantially at a speed a given percentage below that of said rst motor, and adjustable rheostat means disposed between said pilot generator appertaining to said second motor and the appertaining control eld winding of said control generator to permit adjusting said percentage in accordance with a desired percentage of creping.

REST R. BAKER. 

